The present invention relates to a system for controlling the ignition timing of an internal combustion engine such as an automotive engine.
A learning control system for correcting the ignition timing has been proposed. The control system is adapted to advance the ignition timing so as to produce a maximum torque as long as the level of the engine knock does not exceed a tolerable level. The ignition timing stored in a RAM is corrected by a small correcting quantity (quantity of correction) and converged to a desired value little by little. The correcting quantity for the ignition timing at every updating operation is gradually reduced as the ignition timing approaches the desired value.
On the other hand, if a large disturbance, such as change of altitude or change of gasoline to another gasoline having a different octane value, occurs, the ignition timing must be corrected by a large quantity. However, in the state that the ignition timing approaches the desired ignition timing, the correcting quantity at each updating is very small as described above. Accordingly, it takes a long time to correct the ignition timing to a new desired timing.